Stay off the juice for now . . .
Welcome to the board, Destructo.
There are several AS that can alleviate pain. But that is the last thing you want to do right now.
Pain has a purpose - it lets you know how far you can go without going too far. If you mask the pain and push yourself too hard, you can easily make an injury worse. So pain is a way of your body trying to tell you something. Best bet: Listen to your body.
Remember that an AS cycle is only part of the big picture. It does little good on its own; its maximum effects is when you combined it with good workout and diet routines. If any one piece missing, you end up with an incomplete picture.
Sure, you want to go ahead with your planned cycle, but your gear isn't going anywhere. Hold off until your doctgor gives you the all-clear, and that way you won't feel like you have wasted your cycle.
Finally, you may get several pieces of advice as far as what to do about your injury itself. Don't listen to any of it except the advice that says to see a doctor. A muscle/joint/ligament tear is a potentially serious injury, and the only one who can diagnose it and prescribe for it is a physician who has seen you in person. You know our best wishes are with you, but we are not medical experts. This one takes a professional evaluation, probably accompanied by some type of diagnostic testing (X-ray, CT, or MRI).
The most difficult thing you will have to practice here is patience. And many of us know how anxious you must feel. Don't let it get the better of you, and do stay out of the gym until your doctor says it's cool. (In other words, when you start feeling better, don't do too much, too soon, or you'll botch up the healing that has already taken place.) Believe me, once you are ready to go back to your routine, you'll pick up where you left off faster than you think.
So no, deca will not help until you've been evaluated and treated. Yes, your gymnastics are salvagable, but at the moment do it without the roids. However, if you are comfortable with it, ask your doctor about whether he or she thinks roids will help - it's cool, since doctors have to keep your discussions confidential. (But it doesn't hurt to ask the doc not to mention your question in your chart.) Will the injury get worse if you go on a cycle? No, not if you let it heal first, but it can get worse if you don't because you'll get too cocksure and careless, thinking that it is healing when you are actually pushing it too hard.
As for hurting and being scared, welcome to the club, bro. That is the most difficult part of an injury - yes, it can even be worse than the physical pain. But recognize it for what it is - anxiety - and realize that it is perfectly normal. (Hell, I'd worry about you if you weren't scared.) My take, of you play it right: You will get better from this one. And it will most likely be in weeks, not months or years. And when you are better, remember to start back sloooooooooow and easy - you'll pick up your pace fast enough, but don't rush it.
Again, welcome to the A.R. family. See? We like you already, because you seem to be as crazy as the rest of us.